Which would you choose during the holiday shopping season: a long line at the local Costco warehouse store or an average download wait of 115 seconds per page on Costco's e-commerce site?

During Black Friday and Cyber Monday, a third of the 30 Web sites that Keynote Competitive Research monitors during the holiday season showed a significant drop in speed. Online shoppers, despite using high-speed connections, faced up to 2 minutes to process their e-commerce transactions, compared with the 1- to 2-second blip most are accustomed to, according to Keynote, which released its report Tuesday.

Traditional brick-and-mortar retailers that recently beefed up their e-commerce site were the group largely affected with traffic slowdowns, according to the report. And the research firm noted that product searches and check-out transactions were the two areas on sites that were affected the most with sluggish performance.

In Costco's case, for example, its site slowed by as much as 500 percent between 7 a.m. PT and 1 p.m. on Cyber Monday to log on, add items to a shopping cart, and check out, according to the report.

Toys "R" Us suffered as much as a 300 percent slowdown in downloading pages between 10 a.m. PT and 2 p.m. on Cyber Monday, translating to an average wait of 30 seconds to 60 seconds per page. J.Crew experienced a similar slowdown, with the average wait increasing more than 400 percent, according to Keynote. Black Friday and Cyber Monday typically result in a 5 percent to 10 percent increase in site sluggishness, Keynote said.

As you debate the merits of venturing out to hit the local retail stores this holiday season, verses spending a little more time processing transactions online, consider this: which situation affords you more time to eat another Christmas cookie and drink more eggnog?